Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 1

This module introduces the specifics of the most important varieties of Ethernet.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 2

All versions of Ethernet have the same:1. MAC addressing2. CSMA/CD3. Frame format

However, other aspects of the MAC sublayer, physical layer, and medium have changed.

10 0

802.2

Legacy Ethernet

7.1.1 10-Mbps and 100-Mbps Ethernet

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 3

7.1.1 10-Mbps Ethernet

Common timing parameters – all 10 Mbps10BASE2 - 10BASE5 - 10BASE-T

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 4

7.1.1 10-Mbps Ethernet

Common Frame Format

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 5

7.1.1 10-Mbps Ethernet

Differences from higher Bit Rates1. Signal Quality Errors (To tell controller that collision

circuitry is functional)SQE is always used in half-duplex. (Can be used in full-duplex operation but is not required.) www.ethermanage.com/ethernet/sqe/sqe.html

SQE is active: • Within 4 to 8 microseconds following a normal

transmission to indicate that the outbound frame was successfully transmitted.

• Whenever there is a collision on the medium.• Whenever there is an improper signal on the

medium. Improper signals might include jabber, or reflections that result from a cable short.

• Whenever a transmission has been interrupted.

1. Encoding – Manchester2. System Layout (Architecture)

As the frame passes from the MAC sub-layer to the physical layer, speed dependent processes occur prior to the bits being placed from the physical layer

onto the medium.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 6

7.1.1 10-Mbps Ethernet

• No Direct Current• Always a

synchronizing signal

Encoding – Manchester

Simple encodings have undesirable timing and electrical Xtics

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 7

 7.1.2 10BASE5

1. Legacy Ethernet has common architectural features. 2. Networks usually contain multiple types of media. 3. The standard ensures that interoperability is

maintained. 4. The overall architectural design is of the utmost

importance when implementing a mixed-media network.

5. It becomes easier to violate maximum delay limits as the network grows.

6. The timing limits are based on parameters such as: • Cable length and its propagation delay • Delay of repeaters • Delay of transceivers • Inter-frame gap shrinkage • Delays within the station

The main advantages of 10BASE5 were:• It was inexpensive • No configuration was necessary

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 8

• Not more than five segments.• No more than four repeaters may be connected in series

between any two distant stations. • No more than three populated segments.

 7.1.2 10BASE5

The 5-4-3 rule.

no more than 5 segments separated by more than 4 repeaters, and no more than three populated segments

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 9

7.1.3 10BASE2

Thin Net

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 10

7.1.4 10BASE-T

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 11

Signal leaves the NIC and enters the cable on the Orange pair. White-Orange is +ve, solid Orange is

negative.

Signal leaves the cable and enters the NIC on the SPLIT Green pair. White-Green is +ve, solid Green is

negative.

568B

7.1.4 10BASE-T

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 12

7.1.4 10BASE-T

• UTP is cheaper and easier to install• Category 3 and 5 cable are adequate for 10BASE-T networks.• New cable installations use Category 5e or better for multiple protocols.• 10 Mbps of traffic in half-duplex mode and 20 Mbps in full-duplex mode.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 13

7.1.5 10BASE-T wiring and architecture

The 5-4-3 rule still applies.

• 10BASE-T links can have unrepeated distances up to 100 m. • Hubs can solve the distance issue but will allow collisions to

propagate. • The 100 m distance starts over at a Switch.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 14

All versions of Ethernet have the same:1. MAC addressing2. CSMA/CD3. Frame format

However, other aspects of the MAC sublayer, physical layer, and medium have changed.

802.2

Fast Ethernet

7.1 10-Mbps and 100-Mbps Ethernet

10 0

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 15

7.1.6 100-Mbps Ethernet

The only difference between Ethernet and Fast Ethernet is the Bit

Time

The two technologies that have become important are 100BASE-TX, which is a copper UTP medium and 100BASE-FX, which is a multimode optical fiber medium.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 16

7.1.6 100-Mbps Ethernet

The 100-Mbps frame format is the same as the 10-Mbps frame.

• These higher frequency signals are more susceptible to noise. • In response to these issues, two separate encoding steps are used by

100-Mbps Ethernet. 1. The first part of the encoding uses a technique called 4B/5B2. The second part of the encoding is the actual line encoding

specific to copper or fiber.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 17

7.1.7 100BASE-TX/FX

1. The data byte to be sent is first broken into two nibbles. 2. If the byte is 0E, the first nibble is 0 and the second nibble is E. 3. Next each nibble is remapped according to the 4B5B table.

• Hex 0 is remapped to the 4B5B code 11110. • Hex E is remapped to the 4B5B code 11100.

4. In 100BASE-FX and 100BASE-TX, the 4B5B replacement happens at the Physical Coding Sub-layer (PCS)

5. Information is then further encoded for transmission using • MLT-3 in 100BASE-TX at the Physical Medium Dependent

(PMD) sub-layer• NRZI in 100BASE-FX at the Physical Media Attachment (PMA)

sub-layer

4B5B Encoding TableData (Hex) (Binary) 4B5B Code

0 0000 111101 0001 010012 0010 10100... ... ...D 1101 11011E 1110 11100F 1111 11101

There will always be at least one ‘1’ in

each byte, eliminating long strings of zeros.

MULTI-LEVEL TRANSMIT

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 18

7.1.7 100BASE-TX multi-level transmit-3 levels

100BASE-TX (like 100BASE-FX) uses 4B/5B encoding which is then scrambled and converted to multi-level transmit-3 levels or MLT-3.

Any Transition = binary 1.

No transition = binary 0.

Long strings of zeros would give a ‘DC’

component but because of the 4B/5B encoding this can never happen.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 19

7.1.7 100BASE-TX

• 100BASE-TX can be either full-duplex or half-duplex • An Ethernet network using separate transmit and receive wire pairs (full-duplex) and a

switched topology prevents collisions on the physical bus.

MLT3 coding

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 20

7.1.8 100BASE-FX

100BASE-FX (like 100BASE-TX) uses 4B/5B encoding which is then scrambled and converted to Non Return to Zero, Inverted.

Non Return to Zero, Inverted

Any Transition = binary 1.

No transition = binary 0.

Long strings of zeros would give a ‘DC’

component but because of the 4B/5B encoding this can never happen.

Fiber cannot use the 3 level MLT3 because the light source has only two levels, ON and OFF.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 21

7.1.8 100BASE-FX

200 Mbps transmission is possible because of the separate Transmit and Receive paths in 100BASE-FX optical fiber.

• The main application for which 100BASE-FX was designed was inter-building backbone connectivity

• 100BASE-FX was never adopted successfully. This was due to the timely introduction of Gigabit Ethernet copper and fiber standards.

• Gigabit Ethernet standards are now the dominant technology for backbone installations, high-speed cross-connects, and general infrastructure needs.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 22

7.1.8 100BASE-FX

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 23

7.1.8 100BASE-FX

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 24

7.1.9 Fast Ethernet architecture

1. The introduction of switches has made this distance limitation less important.2. If workstations are located within 100 m of a switch, the 100 m distance starts

over at the switch. 3. Since most Fast Ethernet is switched, these are the practical limits between

devices.

A Class I repeater may introduce up to 140 bit-times of latency. Any repeater that changes between one Ethernet implementation and another is a Class I

repeater.

A Class II repeater may only introduce a maximum of 92 bit-times

latency.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 25

7.1.9 Fast Ethernet architecture

1. Only one Class I repeater can be used in a single collision domain.

2. Two Class II repeaters are allowed in a single collision domain, with up to a 5 meter inter-repeater link between them.

3. Class II repeaters are faster than Class I repeaters. 4. This allows Class I repeaters to provide other

services besides simple repeating, such as translating between 100BASE-TX and 100BASE-T4.

5. Class II repeaters are primarily used to link two hubs each supporting only a single implementation of Fast Ethernet.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 26

Fast Ethernet

7.2.1 1000-Mbps Ethernet

Gigabit Ethernet

1000BASE-T inter-switch links are useful for• video streaming applications • server to DAT backup drive links • intra-building backbones

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 27

Once again the frame remains unchanged.

The differences between standard Ethernet, Fast Ethernet and Gigabit Ethernet occur at the physical layer.

• Since the bits are introduced on the medium for a shorter duration and more often, timing is critical.

• This high-speed transmission requires frequencies closer to copper medium bandwidth limitations.

• This causes the bits to be more susceptible to noise on copper media. • Like 100Base-TX these issues require Gigabit Ethernet to use two

separate encoding steps. • Data transmission is made more efficient by using codes to represent

the binary bit stream. • The encoded data provides synchronization, efficient usage of

bandwidth, and improved Signal-to-Noise Ratio characteristics.

To interconnect a 1000BASE-T network to a 100BASE-T network use a layer 2 bridge or switch.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 28

1st Frame

2nd Frame

3rd Frame

4th Frame

• Cat 5e cable can reliably carry up to 125 Mbps of traffic.

• 1000BASE-T uses all four pairs of wires.

• This is done using complex circuitry called a Hybrid to allow full duplex transmissions on the same wire pair.

• This provides 250 Mbps per pair. • With all four-wire pairs, this provides

the desired 1000 Mbps. • Since the information travels

simultaneously across the four paths, the circuitry has to divide frames at the transmitter and reassemble them at the receiver.

Because Gigabit Ethernet is inherently full-duplex, the Media Access Control method views it as a point-to-point

link.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 29

• Fiber cannot do multi level signaling (not 4D-PAM5 nor MLT3)• at 1 Gigabit Non Return to Zero (NRZ) signaling is used with• 8B/10B coding to ensure that a good synchronizing signal is

always present.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 30

Code    GroupName

Actual Byte   BeingEncoded

RD-Encoding        Value

RD+Encoding        Value

Effect onRD afterSending

D1.0 000 00001 011101 0100 100010 1011 same

D4.1 001 00100 110101 1001 001010 1001 flip

D28.5 101 11100 001110 1010 001110 1010 same

D28.5 101 11100 001111 1010 110000 0101 flip

Examples of 8B/10B coding

Features And Operation Of 8B/10B Encoding

Every ten bit code group must fit into one of the following three possibilities:

1. Six ones and four zeros2. Five ones and five zeros 3. Four ones and six zeros

This helps limit the number of consecutive ones and zeros between any two code groups.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 31

Different sub layers in the Physical Layer

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 32

L=Long Wave Length

1300nm

S=Short Wave Length 850

nm

• The Media Access Control method treats the link as point-to-point.

• Since separate fibers are used for transmitting (Tx) and receiving (Rx) the connection is inherently full duplex.

• Gigabit Ethernet permits only a single repeater between two stations.

multimode

error

5000

550

550

550

275

100

25

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 33

Table 1  100BASE-TX, 1000BASE-X, and 1000BASE-T

100BASE-TX 1000BASE-X 1000BASE-T

Frame format 802.3 Ethernet 802.3 Ethernet 802.3 Ethernet

MAC protocol 802.3 Ethernet 802.3 Ethernet 802.3 Ethernet

Flow control 802.3x 802.3x 802.3x

Symbol rate 125 Mbaud 125 Mbaud 1.25 Gbaud

Data rate 100 Mbps 1000 Mbps 1000 Mbps

Encoding (PCS) ANSI FDDI 4B/5B ANSI FC 8B/10B 5 level PAM

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 34

Fast Ethernet

Gigabit Ethernet

All versions of Gigabit Ethernet have the same frame format, timing and transmission

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 35

How does 10GbE compare to other varieties of Ethernet?

1. Frame format is the same, allowing interoperability between all varieties of legacy, fast, gigabit, and 10 Gigabit, with no reframing or protocol conversions.

2. Bit time is now 0.1 nanoseconds. All other time variables scale accordingly.

3. Since only full-duplex fiber connections are used, CSMA/CD is not necessary

4. The IEEE 802.3 sublayers within OSI Layers 1 and 2 are mostly preserved, with a few additions to accommodate 40 km fiber links and interoperability with SONET/SDH technologies.

5. Flexible, efficient, reliable, relatively low cost end-to-end Ethernet networks become possible.

6. TCP/IP can run over LANs, MANs, and WANs with one Layer 2 Transport method.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 36

802.3ae June 2002 10GbE family.

1. 10GBASE-SR – Intended for short distances over already-installed multimode fiber, supports a range between 26 m to 82 m

2. 10GBASE-LX4 – Uses wavelength division multiplexing (WDM), supports 240 m to 300 m over already-installed multimode fiber and 10 km over single-mode fiber

3. 10GBASE-LR and 10GBASE-ER – Support 10 km and 40 km over single-mode fiber

4. 10GBASE-SW, 10GBASE-LW, and 10GBASE-EW – Known collectively as 10GBASE-W are intended to work with OC-192 synchronous transport module (STM) SONET/SDH WAN equipment.

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 37

Physical Media

Dependent

Each transceiver has four 3.125-Gbit/s DFB lasers that are optically multiplexed to provide a 10-Gbit/s data throughput.

10GBASE-LX4 uses Wide Wavelength Division Multiplex (WWDM) to multiplex four bit simultaneous bit streams as four wavelengths of light launched into the fiber at one time.

Physical Media

Attachment

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 38

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 39

7.2.7 Future of Ethernet

1. Copper (up to 1000 Mbps, perhaps more) 2. Wireless (approaching 100 Mbps, perhaps more) 3. Optical fiber (currently at 10,000 Mbps and soon to be more)

Oct-03 ©Cisco Systems CCNA Semester 1 Version 3 Comp11 Mod7 – St. Lawrence College – Cornwall Campus, ON, Canada – Clark slide 40

FIN